Q:What is a Solar Charge Controller? Why do I need one?
A charge controller, or charge regulator is basically a voltage and/or current regulator to keep batteries from overcharging. It regulates the voltage and current coming from the solar panels going to the battery. Most "12 volt" panels put out about 16 to 20 volts, so if there is no regulation the batteries will be damaged from overcharging. Most batteries need around 14 to 14.5 volts to get fully charged.
Q:Do I always need a charge controller?
Not always, but usually. Generally, there is no need for a charge controller with the small maintenance, or trickle charge panels, such as the 1 to 5 watt panels. A rough rule is that if the panel puts out about 2 watts or less for each 50 battery amp-hours, then you don't need one.
Q: Why 12 Volt Solar Panels are 17 Volts?
The obvious question then comes up - "why aren't panels just made to put out 12 volts". The reason is that if you do that, the panels will provide power only when cool, under perfect conditions, and full sun. This is not something you can count on in most places. The panels need to provide some extra voltage so that when the sun is low in the sky, or you have heavy haze, cloud cover, or high temperatures*, you still get some output from the panel. A fully charged "12 volt" battery is around 12.7 volts at rest (around 13.6 to 14.4 under charge), so the panel has to put out at least that much under worst case conditions.
Q: What's A PWM solar charge controller ?
A PWM solar charge controller stands for "Pulse Width Modulation". These operate by making a connection directly from the solar array to the battery bank. During bulk charging, when there is a continuous connection from the array to the battery bank, the array output voltage is 'pulled down' to the battery voltage. As the battery charges, the voltage of the battery rises, so the voltage output of the solar panel rises as well, using more of the solar power as it charges. As a result, you need to make sure you match the nominal voltage of the solar array with the voltage of the battery bank. *Note that when we refer to a 12V solar panel, that means a panel that is designed to work with a 12V battery. The actual voltage of a 12V solar panel, when connected to a load, is close to 18 Vmp (Volts at maximum power). This is because a higher voltage source is required to charge a battery. If the battery and solar panel both started at the same voltage, the battery would not charge.
Q: What's MPPT solar charge controller ?
An MPPT solar charge controller stands for "Maximum Power Point Tracking". It will measure the Vmp voltage of the panel, and down-converts the PV voltage to the battery voltage. Because power into the charge controller equals power out of the charge controller, when the voltage is dropped to match the battery bank, the current is raised, so you are using more of the available power from the panel. You can use a higher voltage solar array than battery, like the 60 cell nominal 20V grid-tie solar panels that are more readily available. With a 20V solar panel, you can charge a 12V battery bank, or two in series can charge up to a 24V battery bank, and three in series can charge up to a 48V battery bank. This opens up a whole wide range of solar panels that now can be used for your off-grid solar system.
Q: What are the pros and cons for PWM solar charge controller and MPPT solar charge controller ?
1.PWM charge controller are built on a time tested technology.They have been used for years and are well established.
2.These charge controllers are inexpensive.
3.PWM charge controllers are avaialble in sizes up to 60 amps.
4.PWM charge controllers are durable , most with passive heat sink style cooling.
5.These charge controllers are available in many sizes for a variety of applications.
1.The PV input nominal voltage must match battery bank nominal voltage if you're going to use PWM.
2.There is no single controller sized over 60 amps DC as of yet.
3.Many smaller PWM charge controller units are not UL listed.
4.Many smaller PWM charge controller units come without fittings for conduit.
5.PWM charge controllers have limited capacity for system growth.
1.MPPT charge controllers offer a potential increase in charging efficiency up to 30 %.
2.These charge controllers also offer the potential ability to have array with higher input voltage than battery bank.
3.You can get sizes up to 100 amps .
4.MPPT charge controller warranties are typically longer than PWM units.
5.MPPT offer great flexibility for system growth.
1.MPPT charge controllers are expensive.
2.MPPT units are generally larger in physical size.
3.Sizing an appropriate PV array can be challenging without MPPT charge controller manufacturer guides.
4.Using an MPPT controller forces the PV array to be comprised of like photovoltaic modules in like strings.
Q: What's the summary of comparison between PWM and MPPT solar charge controller ?
PWM Charge Controller
MPPT Charge Controller
PV & battery voltages should match
PV can be higher than battery voltage
Operates at battery voltage so it performs well in warm temperatures and when the battery is almost full
Operates above battery voltage so it is can provide "boost" in cold temperatures and when the battery is low.
Recommended for use in smaller systems where MPPT benefits areminimal
150W – 200W or higher to take advantage of MPPT benefits
Off-Grid or Grid-Tie
Must use off-grid PV modules typically with Vmp ≈ 17 to 18 Volts for every 12V nominal battery voltage
Enables the use of lower cost/grid-tie PV Modules helping bring down the overall PV system cost
Array Sizing Method
PV array sized in Amps (based on current produced when PV array is operating at battery voltage)
PV array sized in Watts (based on the Controller Max. Charging Current x Battery Voltage)
Notes: The Vmp (maximum power voltage) is the voltage where the product of the output current and output voltage (amps * volts) is greatest and output power (watts = amps * volts) is maximized. Module wattage ratings (e.g. 100W, 205W) are based on Pmp (maximum power) at Vmp under standard test conditions (STC).
Company: Qingdao Hinergy New Energy CO.,LTD
Contact: Jackie Chen
WhatsApp/Wechat:+86 135 8929 9688